This is a model of the bottom part of the housing of the Smart Sony Tennis Sensor, made with OpenSCAD.

This tennis sensor, introduced by Sony in 2014 and discontinued in 2016, is a cool and useful device. It is known to have problems with battery and with the bottom part of the housing, which is also the mounting lug, cracking into pieces. The battery can be replaced (order CP1254 and solder it), and here it the replacement for the cracking housing! If printed using SLS (selective laser sintering) from Nylon 12, it is both strong and accurate enough to replace the original housing. My impression is that it is actually stronger than the original one, and nylon is known to be crack-resistant, so it should hold better than the original one. I have been able to successfully repair two sensors with this part, and both work well! Here is how it looks like: